The minimal clearance for WSF is 0.5 mm.
But it is usually wise to avoid large surface with near contact for with moving parts.
As this increases the chances of powder jamming up or causing to much friction.

By no means is WSF the only material which you can do moving parts. Sandstone, and all the "Detail" materials (and some others) can have moving parts as well.
On each of the materials pages, you can see what the minimum clearance is and/or whether that material support "interlocking" parts.

Patience, Persistance, Politeness - the 3Ps will help us get us to Perfect Printed Products